Hydrotreating catalyst composition and processes therefor and therewith

ABSTRACT

A catalyst composition and a process for converting a hydrocarbon stream such as, for example, a C 9  +aromatic compound to C 6  to C 8  aromatic hydrocarbons such as xylenes are disclosed. The catalyst composition comprises an aluminosilicate, and a metal wherein the weight ratio of aluminum to silicon is in the range of from about 0.002:1 to about 0.6:1. The process comprises contacting a hydrocarbon stream with the catalyst composition under a condition sufficient to effect the conversion of a hydrocarbon to a C 6  to C 8  aromatic hydrocarbon. Also disclosed is a process for producing the catalyst composition which comprises: (1) optionally contacting a beta zeolite with steam to produce a steamed beta zeolite; (2) contacting a beta zeolite or the steamed beta zeolite with an effective amount of an acid under a condition sufficient to effect a reduction in aluminum content of the beta zeolite to produce an acid-leached beta zeolite; and (3) impregnating the acid-leached beta zeolite with an effective amount of a metal compound under a condition sufficient to effect the production of a metal-promoted beta zeolite.

This application is a division of application Ser. No. 08/791,426, filedJan. 30, 1997 now U.S. Pat. No. 5,866,744, abandoned.

FIELD OF THE INVENTION

This invention relates to a catalyst composition useful for converting ahydrocarbon to a C₆ to C₈ aromatic hydrocarbon, to a process forproducing the composition, and to a process for using the compositionfor converting a hydrocarbon to a C₆ to C₈ aromatic hydrocarbon.

BACKGROUND OF THE INVENTION

It is well known to those skilled in the art that aromatic hydrocarbonsare a class of very important industrial chemicals which find a varietyof uses in petrochemical industry. It is also well known to thoseskilled in the art that catalytically cracking gasoline-rangehydrocarbons produces aromatic hydrocarbons such as, for example,benzene, toluene, and xylenes (hereinafter collectively referred to asBTX) in the presence of catalysts which contain a zeolite. The productof this catalytic cracking process contains a multitude of hydrocarbonsincluding unconverted C₅ +alkanes, C₅ +alkenes, C₅ +cycloalkanes, orcombinations of two or more thereof, lower alkanes such as methane,ethane, and propane; lower alkenes such as ethylene and propylene; andC₉ +aromatic compounds having 9 or more carbon atoms per molecule.Recent efforts to convert gasoline to more valuable petrochemicalproducts have focused on improving the conversion of gasoline to morevaluable aromatic hydrocarbons in the presence of zeolite catalysts. Forexample, a gallium-promoted zeolite ZSM-5 has been used in the so-calledCyclar Process to convert a hydrocarbon to BTX. The aromatichydrocarbons can be useful feedstocks for producing various organiccompounds and polymers. However, heavier, less useful aromatic compoundshaving 9 or more carbon atoms per molecule (C₉ +aromatic compounds) arealso produced by the conversion process. Furthermore, a zeolite catalystis generally deactivated in a rather short period, especially in a highsulfur and/or polyaromatics environment, because of depositions ofcarbonaceous material, generally coke, on the surface of the catalyst.Therefore, development of a catalyst and a process for converting a C₉+aromatic compound to the more valuable BTX in which the process andcatalyst reduce the depositions of the carbonaceous material would be asignificant contribution to the art and to the economy.

SUMMARY OF THE INVENTION

An object of this invention is to provide a catalyst composition whichcan be used to convert a hydrocarbon to a C₆ to C₈ aromatic hydrocarbon.Also an object of this invention is to provide a process for producingthe catalyst composition. Another object of this invention is to providea process which can employ the catalyst composition to convert ahydrocarbon to a C₆ to C₈ aromatic hydrocarbon. An advantage of thecatalyst composition is that it enhances the production of BTX andsuppresses the deposition of coke thereon. Other objects and advantageswill becomes more apparent as this invention is more fully disclosedhereinbelow.

According to a first embodiment of the present invention, a compositionwhich can be used as a catalyst for converting a hydrocarbon or ahydrocarbon mixture to a C₆ to C₈ aromatic hydrocarbon is provided. Thecomposition comprises, consists essentially of, or consists of, acrystalline aluminosilicate and a metal selected from the groupconsisting of nickel, palladium, molybdenum, gallium, platinum, copper,chromium, rhodium, rhenium, tungsten, cobalt, germanium, zirconium,titanium, ruthenium, and combinations of any two or more thereof.

According to a second embodiment of the present invention, a processwhich can be used for producing a catalyst composition is provided. Theprocess comprises the steps: (1) contacting a zeolite, which comprises,consists essentially of, or consists of, silicon, aluminum, and oxygen,with steam, under a condition sufficient to effect the production of azeolite having a reduced coking rate in a transalkylation process,whereby a steamed zeolite is formed; (2) optionally, contacting saidsteamed zeolite with an acid in an amount and under a conditioneffective to reduce the aluminum content of the zeolite to produce anacid-leached zeolite; (3) contacting the steamed zeolite or theacid-leached zeolite with a metal compound whose metal is selected fromthe group consisting of nickel, palladium, molybdenum, gallium,platinum, tin, chromium, rhodium, rhenium, tungsten, indium, cobalt,germanium, zirconium, titanium, ruthenium, and combinations of any twoor more thereof under a condition effective to incorporate the metalcompound or the metal into the steamed zeolite or the acid-leachedzeolite to produce a metal-incorporated zeolite; and (4) optionallytreating the metal-incorporated zeolite with a reducing agent under acondition effective to lower the oxidation state of the metal in themetal-promoted zeolite.

According to a third embodiment of the present invention, a process,which can be used for converting a hydrocarbon or a hydrocarbon mixtureto a C₆ to C₈ aromatic hydrocarbon and for reducing the deposition ofcarbonaceous material on the surface of a catalyst is provided whichcomprises, consists essentially of, or consists of, contacting a fluidwhich comprises a hydrocarbon or a hydrocarbon mixture with a catalystcomposition which can be the same as disclosed above in the firstembodiment and can be made by the process disclosed above in the secondembodiment of the invention under a condition effective to convert ahydrocarbon to an aromatic hydrocarbon containing 6 to 8 carbon atomsper molecule.

DETAILED DESCRIPTION OF THE INVENTION

The catalyst composition of the first embodiment of the presentinvention comprises a crystalline aluminosilicate and a metal selectedfrom the group consisting of nickel, palladium, molybdenum, gallium,platinum, chromium, rhodium, rhenium, tungsten, cobalt, germanium,zirconium, titanium, ruthenium, and combinations of any two or morethereof. The metal can be, and generally is chemically bonded to oxygenor sulfur.

According to the present invention, the term "coke" refers to asemi-pure carbon generally deposited on the surface of a metal wall or acatalyst. The term "hydrocarbon" generally has the formula of RH_(z) inwhich R is a hydrocarbyl radical having 1 to about 30, preferably 5 toabout 25, and most preferably 9 to 16 carbon atoms per molecule; z is anumber that fills the necessary valency of R; and the hydrocarbylradicals can be alkyl radical, aryl radical, alkaryl radical, aralkylradical, or combinations of any two or more thereof and can besubstituted or unsubstituted.

The weight ratio of aluminum to silicon of the crystallinealuminosilicate can be any ratio that is effective to convert ahydrocarbon to an aromatic hydrocarbon. Generally, the weight ratio ofelement aluminum to element silicon can be in the range of from about0.002:1 to about 0.6:1, preferably about 0.005:1 to about 0.5:1, andmost preferably 0.006:1 to 0.4:1. The weight ratio of the incorporatedmetal to element silicon can be any ratio that can enhance theconversion of a hydrocarbon to a BTX and can be in the range of fromabout 0.0001:1 to about 0.1:1, preferably about 0.0005:1 to about0.05:1, more preferably about 0.001:1 to about 0.04:1, and mostpreferably 0.002:1 to 0.03:1.

Alternatively, the weight of element aluminum in the inventioncomposition can be in the range of from about 0.1 to about 20,preferably about 0.5 to about 15, and most preferably 0.5 to 10 gramsper 100 grams of the composition. The weight of element silicon in theinvention composition can be in the range of from about 10 to about 50,preferably about 15 to about 40, and most preferably 20 to 40 grams per100 grams of the composition. The weight of the incorporated metal canbe such that is effective to enhance the conversion of a hydrocarbon toBTX and can be in the range of from about 0.001 to about 15, preferablyabout 0.01 to about 10, and most preferably 0.1 to 5 grams per 100 gramsof the composition. The composition can also be characterized by havingthe following physical characteristics: a micropore surface area, asdetermined by the BET method using nitrogen, in the range of from about50 to about 1,000, preferably to 500 m² /g; a micropore pore volume inthe range of from about 0.1 to about 2.0, preferably about 0.1 to about1.0 ml/g; an average micropore pore diameter in the range of from about0.1 to about 500, preferably about 1 to about 200 Å; and a porosity ofmore than about 20%.

The aluminosilicate or zeolite component of the composition of thepresent invention can be prepared by combining any alumina and anysilica in the element weight ratios disclosed above under any conditionssufficient to effect the formation of a zeolite according to any methodswell known to one skilled in the art. However, it is presently preferredthat the composition of the present invention be produced by the processdisclosed in the second embodiment of the invention.

Any commercially available zeolites can be employed as a startingmaterial of the process of the second embodiment of the invention.Examples of suitable zeolites include, but are not limited to, thosedisclosed in Kirk-Othmer Encyclopedia of Chemical Technology, thirdedition, volume 15 (John Wiley & Sons, New York, 1991). The presentlypreferred zeolite is a beta zeolite, especially one having a frameworktopology identified as BEA because it is highly acidic andshape-selective.

According to the second embodiment of the invention, a zeolite,preferably a beta zeolite, can be optionally contacted with one or moresuitable binders in a liquid, preferably aqueous medium, to form azeolite-binder mixture. Any binders known to one skilled in the art foruse with a zeolite are suitable for use herein. Examples of suitablebinder include, but are not limited to, clays such as for example,kaolinite, halloysite, vermiculite, chlorite, attapulgite, smectite,montmorillonite, illite, saconite, sepiolite, palygorskite, diatomaceousearth, and combinations of any two or more thereof; aluminas such as forexample α-alumina and γ-alumina; silicas; alumina-silica; aluminumphosphate; aluminum chlorohydrate; and combinations of any two or morethereof. Because these binders are well known to one skilled in the art,description of which is omitted herein. The weight ratio of a zeolite toa binder can be in a wide range and generally in the range of from about200:1 to about 0.1:1, preferably 100:1 to 0.01:1.

The zeolite and the binder can be well mixed by any means known to oneskilled in the art such as stirring, blending, kneading, or extrusion,following which the zeolite-binder mixture can be dried in air at atemperature in the range of from about 20 to about 200° C., preferablyabout 25 to about 175° C., and most preferably 25 to 150° C. for about0.5 to about 50 hours, preferably about 1 to about 30 hours, and mostpreferably 1 to 20 hours, preferably under atmospheric pressure.Thereafter, the dried, zeolite-binder mixture can be further calcined,if desired, in air at a temperature in the range of from about 300 to1000° C., preferably about 350 to about 750° C., and most preferably 450to 650° C. to prepare a calcined zeolite-binder. If a binder is notdesired, a zeolite can also be calcined under similar conditions toremove any contaminants, if present.

A zeolite, a calcined zeolite, or a calcined zeolite-binder can betreated with a compound containing an exchangeable ammonium ion toprepare an ammonium-exchanged zeolite. Whether a zeolite is calcined orcontains a binder, the process or treatment in the second embodiment isthe same for each. For the interest of brevity, only a zeolite isdescribed hereinbelow. Examples of suitable ammonium-containingcompounds include, but are not limited to, ammonium sulfate, ammoniumchloride, ammonium nitrate, ammonium bromide, ammonium fluoride, andcombinations of any two or more thereof. Treatment of the zeolitereplaces the original ions such as, for example, alkali or alkalineearth metal ions of the zeolite with predominantly ammonium ions.Techniques for such treatment are well known to one skilled in the artsuch as, for example, ion exchange with the original ions. For example,a zeolite can be contacted with a solution containing a salt of thedesired replacing ion or ions.

Generally, a zeolite can be suspended in an aqueous solution of anammonium-containing compound. The concentration of the zeolite in theaqueous solution can be in the range of from about 0.01 to about 200,preferably about 0.1 to about 150, more preferably about 1 to about 100,and most preferably 5 to 75 grams per liter. The amount of theammonium-containing compound required depends on the amount of theoriginal ion(s) to be exchanged. Upon the preparation of the solution,the solution can be subject to a temperature in the range of from about30° C. to about 200° C., preferably about 40° C. to about 150° C., andmost preferably 50° C. to 125° C. for about 1 to about 100 hours,preferably about 1 to about 50 hours, and most preferably 2 to 25 hoursdepending on desired degrees of ion exchange. The treatment can becarried out under a pressure in the range of from about 1 to about 10atmospheres (atm), preferably about 1 atm or any pressure that canmaintain the required temperature. Thereafter, the treated zeolite canbe washed with running water for 1 to about 60 minutes followed bydrying and calcining to produce calcined zeolite. The drying andcalcining processes can be carried out substantially the same as thosedisclosed above for the preparation of a calcined zeolite orzeolite-binder.

Generally, the ammonium-exchanged zeolite becomes hydrogen exchangedupon calcination or high temperature treatment such that a predominantproportion of its exchangeable cations are hydrogen ions. Theabove-described ion exchanges of exchangeable ions in a zeolite is wellknown to one skilled in the art. See, for example, U.S. Pat. No.5,516,956, disclosure of which is incorporated herein by reference.Because the ion exchange procedure is well known, the description ofwhich is omitted herein for the interest of brevity.

In the first step of the second embodiment of the invention, a zeolitein a desired ionic form, regardless whether calcined or containing abinder, can be contacted with steam under a condition sufficient toeffect the formation of steamed zeolite. Generally the steam temperaturecan be in the range of from about 120° C. to about 1500° C., preferablyabout 200° C. to about 1000° C., more preferably 250° C. to 800° C., andmost preferably 350 to 625° C. The contact period can be as short as 5minutes to as long as about 30 hours, preferably about 30 minutes to 20hours, and most preferably 1 hour to 10 hours. The treatment can becarried out under a pressure that can maintain or accommodate the steamtemperature in the range of from about atmospheric pressure to about2,000, preferably to about 1,500, and most preferably to 1000 psig.

Upon completion of steam treatment, a steamed zeolite is formed whichcan be treated with an acid. Generally, any organic acids, inorganicacids, or combinations of any two or more thereof can be used in theprocess of the present invention so long as the acid can reduce thealuminum content in the zeolite. The acid can also be a diluted aqueousacid solution. Examples of suitable acids include, but are not limitedto sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid,formic acid, acetic acid, trifluoroacetic acid, trichloroacetic acid,p-toluenesulfonic acid, methanesulfonic acid, partially neutralizedacids wherein one or more protons have been replaced with, for example,a metal (preferably an alkali metal) or ammonium ion, and combinationsof any two or more thereof. Examples of partially neutralized acidsinclude, but are not limited to, sodium bisulfate, sodium dihydrogenphosphate, potassium hydrogen tartarate, ammonium sulfate, ammoniumchloride, ammonium nitrate, and combinations thereof. The presentlypreferred acids are hydrochloric acid and nitric acid for they arereadily available.

Any methods known to one skilled in the art for treating a solidcatalyst with an acid can be used in the acid treatment of the presentinvention. Generally, a zeolite material can be suspended in an acidsolution. The concentration of the zeolite in the acid solution can bein the range of from about 0.01 to about 500, preferably about 0.1 toabout 400, more preferably about 1 to about 350, and most preferably 5to 300 grams per liter. The amount of acid required is the amount thatcan maintain the solution in acidic pH during the treatment. Preferablythe initial pH of the acid solution containing a zeolite is adjusted tolower than about 6, preferably lower than about 5, more preferably lowerthan about 4, and most preferably lower than 3. Upon the pH adjustmentof the solution, the solution can be subjected to a treatment at atemperature in the range of from about 30° C. to about 200° C.,preferably about 50° C. to about 150° C., and most preferably 70° C. to120° C. for about 10 minutes to about 30 hours, preferably about 20minutes to about 25 hours, and most preferably 30 minutes to 20 hours.The treatment can be carried out under a pressure in the range of fromabout 1 to about 10 atmospheres (atm), preferably about 1 atm so long asthe desired temperature can be maintained. Thereafter, the acid-treatedzeolite material can be washed with running water for 1 to about 60minutes followed by drying, at about 50 to about 1000, preferably about75 to about 750, and most preferably 100 to 650° C. for about 0.5 toabout 15, preferably about 1 to about 12, and most preferably 1 to 10hours, to produce an acid-leached zeolite. Any drying method known toone skilled in the art such as, for example, air drying, heat drying,spray drying, fluidized bed drying, or combinations of two or morethereof can be used.

The dried, acid-leached zeolite can also be further washed, if desired,with a mild acid solution such as, for example, ammonium nitrate whichis capable of maintaining the pH of the wash solution in acidic range.The volume of the acid generally can be the same volume as the acid forreducing the alumina content in a zeolite. The mild acid treatment canbe carried out under substantially the same conditions disclosed in theacid treatment for reducing alumina content in a zeolite. Thereafter,the resulting solid can be washed and dried as disclosed above.

The dried, acid-leached zeolite, whether it has been further washed witha mild acid or not, can be calcined, if desired, under a condition knownto those skilled in the art. Generally such a condition can include atemperature in the range of from about 250 to about 1,000, preferablyabout 350 to about 750, and most preferably 450 to 650° C. and apressure in the range of from about 0.5 to about 50, preferably about0.5 to about 30, and most preferably 0.5 to 10 atmospheres (atm) forabout 1 to about 30 hours, preferably about 2 to about 20 hours, andmost preferably 3 to 15 hours.

Thereafter, the steamed zeolite or acid-leached zeolite, whether it hasbeen calcined or not, can be incorporated therein or impregnated thereonwith a metal compound whose a metal selected from the group consistingof nickel, palladium, molybdenum, gallium, platinum, tin, chromium,rhodium, rhenium, tungsten, indium, cobalt, germanium, zirconium,titanium, ruthenium, and combinations of any two or more thereof. Anymetal compound that can promote the incorporating or impregnating of theacid-leached zeolite with the metal of the metal compound can beemployed in the present invention.

Generally, any platinum-containing compound that can promote thecombining of platinum element with an aluminosilicate can be employedherein. Examples of suitable platinum-containing compounds include, butare not limited to, chloroplatinic acid (H₂ PtCl₆.xH₂ O), platinum (IV)chloride (platinic chloride), platinum (II) bromide, platinum (II)iodine, tetramine platinum (II) chloride (Pt(NH₃)₄ Cl₂.H₂ O or Pt(NH₃)₄Cl₂), tetramine platinum (II) nitrate (Pt(NH₃)₄ (NO₃)₂), tetramineplatinum (II) hydroxide (Pt(NH₃)₄ (OH)₂), tetrachlorodiamine platinum(IV), and combinations of any two or more thereof. The presentlypreferred platinum-containing compound is chloroplatinic acid for it isreadily available.

Similarly, examples of suitable tin-containing compound include, but arenot limited to, stannous acetate, stannic acetate, stannous bromide,stannic bromide, stannous chloride, stannic chloride, stannous oxalate,stannous sulfate, stannic sulfate, stannous sulfide, and combinations ofany two or more thereof.

Examples of suitable titanium-containing compounds include, but are notlimited to, zinc titanate, lanthanum titanate, titanium tetramides,titanium tetramercaptides, titanium tetrabutoxide, titaniumtetramethoxides, titanium tetraethoxide, titanium tetrapropoxide,titanium tetrachloride, titanium trichloride, titanium bromides, andcombinations of any two or more thereof.

Similarly, examples of suitable zirconium-containing compounds include,but are not limited to, zirconium acetate, zirconium formate, zirconiumchloride, zirconium bromide, zirconium butoxide, zirconiumtert-butoxide, zirconium citrate, zirconium ethoxide, zirconiummethoxide, zirconium propoxide, and combinations of any two or morethereof.

Examples of suitable germanium-containing compounds include, but are notlimited to, germanium chloride, germanium bromide, germanium ethoxide,germanium fluoride, germanium iodide, germanium methoxide, andcombinations of any two or more thereof.

Examples of suitable indium-containing compounds include, but are notlimited to indium acetate, indium bromide, indium chloride, indiumfluoride, indium iodide, indium nitrate, indium phosphide, indiumselenide, indium sulfate, and combinations of any two or more thereof.

Examples of suitable lanthanum-containing compounds include, but are notlimited to, lanthanum acetate, lanthanum carbonate, lanthanum octanoate,lanthanum fluoride, lanthanum chloride, lanthanum bromide, lanthanumiodide, lanthanum nitrate, lanthanum perchlorate, lanthanum sulfate,lanthanum titanate, and combinations of any two or more thereof.

Examples of other suitable metal compounds include, but are not limitedto, molybdenum(II) acetate, ammonium molybdate, ammonium dimolybdate,ammonium heptamolybdate, phosphomolybdic acid, molybdenum(III) bromide,molybdenum(II) chloride, molybdenum(IV) chloride, molybdenum(V)chloride, molybdenum hexacarbonyl, molybdenum(IV) sulfide, sodiummolybdate, potassium molybdate, molybdenum oxychloride, molybdenumfluoride, molybdenum(VI) tetrachloride oxide, ammoniumtetrathiomolybdate, chromium(II) acetate, chromium(III) acetate,chromium(III) acetylacetonate, chromium(II) chloride, chromium(III)chloride, chromium(II) fluoride, chromium(III) fluoride, chromiumhexacarbonyl, chromium(III) nitrate, chromium nitride, chromium(III)2,4-pentanedionate, chromium(III) perchlorate, chromium(III) potassiumsulfate, chromium(III) sulfate, chromium(III) telluride, cobalt(II)acetate, cobalt(II) acetylacetonate, cobalt(III) acetylacetonate,cobalt(II) benzoylacetonate, cobalt(II) bromide, cobalt(II) carbonate,cobalt(II) chloride, cobalt(II) 2-ethylhexanoate, cobalt(II) fluoride,cobalt(III) fluoride, cobalt(II) iodide, cobalt(II) iodide, cobalt(II)2,3-naphthalocyanine, cobalt(II) nitrate, cobalt(II) oxalate, cobalt(II)perchlorate, cobalt(II) phthalocyanine, cobalt(II) sulfate, cobalt(II)thiocyanate, cobalt(II) tungstate, nickel(II) acetate, nickel(II)acetylacetonate, nickel(II) bromide, nickel(II) carbonate, nickel(II)chloride, nickel(II) nitrate, nickel(II) perchlorate, nickel phosphide,nickel(II) sulfate, nickel sulfide, nickel(II) titanate, palladium(II)acetate, palladium(II) acetylacetonate, palladium(II) bromide,palladium(II) iodide, palladium(II) nitrate, palladium(II) sulfate,palladium(II) sulfide, rhodium(II) acetate, rhodium(III)acetylacetonate, rhodium(III) bromide, rhodium(III) chloride,rhodium(III) nitrate, rhodium(II) octanoate, rhodium(III) phosphate,rhodium(III) sulfate, rhenium nitrate, rhenium sulfate, tungsten(V)bromide, tungsten(IV) chloride, tungsten(VI) chloride, tungstenhexacarbonyl, tungsten(VI) oxychloride, tungsten(IV) sulfide, tungsticacid, and combinations of any two or more thereof.

The presently preferred metal compound is an ammonium molybdate for itis readily available and effective for incorporating Mo into a zeolite.

A metal-promoted or metal-impregnated zeolite can be prepared by anysuitable, effective means so long as the resulting zeolite can be usedin the process of the present invention. Preferably, a zeolite oracid-leached zeolite, which can have been compounded with a binder asdescribed above and have been shaped by any means known in the art suchas, for example, pelletized, extruded, tableted, or combinations of twoor more thereof, can be impregnated such as, for example, by incipientwetness method with a solution, preferably aqueous solution, containinga suitable metal compound disclosed above under a condition well knownto one skilled in the art such as, for example, at about 25° C. forabout 1 minute to about 10 hours under atmospheric pressure. Theconcentrations of the metal compound in the impregnating solution andthe weight ratio of this solution to the zeolite are chosen such as toprovide a finished, metal-impregnated, acid-leached zeolite whichcontains the desired content of metal which can effect the reduction ofcoke deposition on the surface of the composition of the presentinvention as disclosed above in the first embodiment of the presentinvention. Because the impregnation process is well known to one skilledin the art, the description of which is omitted herein.

After the incorporation or impregnation with a metal compound has beencompleted, the metal-impregnated zeolite can then be dried, as disclosedabove and then calcined. Generally the calcination is carried out in airunder the pressure range disclosed above for calcining the acid-leachedzeolite. The calcination can also be carried out at a temperature in therange of about 300 to about 1000° C. for about 1 to about 30 hours,preferably about 400° C. to about 800° C. for 1 to about 20 hours, andmost preferably 450° C. to 650° C. for 2 to 15 hours.

The calcined, metal-impregnated zeolite can then be treated with areducing agent to reduce the oxidation state of the metal. For example,if the metal is platinum, the oxidation state of platinum can be reducedto 0. The presently preferred reducing agent is a hydrogen-containingfluid which comprises molecular hydrogen (H₂) in the range of from 1 toabout 100, preferably about 5 to about 100, and most preferably 10 to100 volume %. The reduction can be carried out at a temperature, in therange of from about 250° C. to about 800° C. for about 0.1 to about 10hours preferably about 300° C. to about 700° C. for about 0.5 to about 7hours, and most preferably 350° C. to 550° C. for 1 to 5 hours. If thecalcined, metal-impregnated zeolite is not first treated with a reducingagent, the composition of the present invention can be treated with areducing agent as described herein prior to use of the composition ofthe invention.

Upon completion of the above-described treatment or impregnation of anacid-leached zeolite with a metal compound, a metal-promoted zeolitecomposition is produced which can then be used in the third embodimentof the present invention.

According to the third embodiment of the present invention, a processuseful for converting a hydrocarbon, preferably a C₉ +aromatic compound,to a mixture rich in C₆ to C₈ aromatic hydrocarbons comprises, consistsessentially of, or consists of contacting a fluid stream with a catalystcomposition, optionally in the presence of an inert gas or ahydrogen-containing fluid, under a condition sufficient to enhance oreffect the conversion of a hydrocarbon to a mixture rich in C₆ to C₈aromatic hydrocarbons wherein said fluid stream comprises a hydrocarbonor hydrocarbon mixture which can comprise C₉ +aromatic compounds,paraffins, olefins, naphthenes. The catalyst composition is the same asthat disclosed in the first embodiment of the invention which can beprepared by the second embodiment of the invention.

The term "fluid" is used herein to denote gas, liquid, vapor, orcombinations thereof. The term "enhance" refers to an increased BTX inthe product employing the catalyst composition as compared to employingan untreated zeolite. Examples of a hydrocarbon include, but are notlimited to, butane, isobutanes, pentane, isopentanes, hexane,isohexanes, cyclohexane, methylcyclohexane, heptane, isoheptanes,octane, isooctanes, nonanes, decanes, undecanes, dodecanes, tridecanes,tetradecanes, pentadecanes, hexadecanes, butenes, isobutene, pentenes,hexenes, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene,1,3,5-trimethylbenzene, 1,2,3,4-tetramethylbenzene,1,2,3,5-tetramethylbenzene, 1,2,4,5-tetramethylbenzene, n-propylbenzene,3-ethyltoluene, 4-ethyltoluene, 3-n-propyltoluene, 4-n-propyltoluene,1,3-diethylbenzene, naphthalenes, and combinations of any two or morethereof. In some feed fluids, such as, for example, gasoline cancomprise some benzene, toluene, ethylbenzene, and xylenes.

Any fluid which contains a C₉ +aromatic compound can be used as the feedfor the process of this invention. Generally, the fluid feed stream canalso contain olefins, naphthenes (cycloalkanes), or some aromaticcompounds. Examples of suitable, available fluid feeds include, but arenot limited to, gasolines from catalytic oil cracking processes,pyrolysis gasolines from thermal cracking of saturated hydrocarbons,naphthas, gas oils, reformates, and combinations of any two or morethereof. The origin of this fluid feed is not critical. Thoughparticular composition of a feed is not critical, a preferred fluid feedis derived from gasolines which generally contain more paraffins(alkanes) than combined content of olefins, cycloalkanes, and aromaticcompounds.

Any fluid which contains a C₉ +aromatic compound as disclosed above canalso be used as the feed for the process of this invention. A C₉+aromatic compound can have the formula of R'_(q) Ar wherein each R' isa hydrocarbyl radical having 1 to about 15 carbon atoms and isindependently selected from the group consisting of alkyl radicals, arylradicals, alkaryl radicals, aralkyl radicals, alkenyl radicals, andcombinations of any two or more thereof, q is a whole number from 1 to5, and Ar is a phenyl group. The origin of the C₉ +aromatic compoundsfeed is not critical. However, a preferred fluid feed is a C₉ +aromaticcompound derived from the heavies fraction of a product from a paraffin,in particular gasoline, aromatization reaction. Generally, this heaviesfraction contains primarily trimethylbenzenes such as1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, and1,3,5-trimethylbenzene; tetramethylbenzenes such as1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene and1,2,4,5-tetramethylbenzene; and naphthalenes. Additionally,n-propylbenzene, 3-ethyltoluene, 4-ethyltoluene, 3-n-propyltoluene,4-n-propyltoluene, and 1,3-diethylbenzene can also be present in thefluid.

In a hydrodealkylation process benzene, toluene, ethylbenzene andxylenes are generally substantially absent from the fluid, i.e., theamount of each of these aromatic hydrocarbons is less than about 0.1weight % in the fluid. However, in a transalkylation process, one ormore of benzene, toluene, ethylbenzene and xylenes can be present in thefeed to effect a significant alkylation of the lower aromatichydrocarbons by the C₉ +aromatic compounds, i.e., significanttransalkylation occurs. The condition for carrying out hydrodealkylationand transalkylation can be substantially the same as disclosedhereinbelow.

Any hydrogen-containing fluid which comprises, consists essentially of,or consists of, molecular hydrogen (H₂) can be used in the process ofthis invention. This hydrogen-containing fluid can therefore contain H₂in the range of from about 1 to about 100, preferably about 5 to about100, and most preferably 10 to 100 volume %. If the H₂ content in thefluid is less than 100%, the remainder of the fluid may be any inert gassuch as, for example, N₂, He, Ne, Ar, steam, or combinations of any twoor more thereof, or any other fluid which does not significantly affectthe process or the catalyst composition used therein.

The contacting of a fluid feed stream containing a hydrocarbon with ahydrogen-containing fluid in the presence of the catalyst compositioncan be carried out in any technically suitable manner, in a batch orsemicontinuous or continuous process, under a condition effective toconvert a hydrocarbon to a C₆ to C₈ aromatic hydrocarbon. Generally, afluid stream as disclosed above, preferably being in the vaporizedstate, is introduced into a suitable hydroprocessing reactor having afixed catalyst bed, or a moving catalyst bed, or a fluidized catalystbed, or combinations of any two or more thereof by any means known toone skilled in the art such as, for example, pressure, meter pump, andother similar means. Because a hydroprocessing reactor and processtherewith are well known to one skilled in the art, the description ofwhich is omitted herein for the interest of brevity. The condition ofthe process of the invention can include a weight hourly space velocityof the fluid feed stream in the range of about 0.01 to about 100,preferably about 0.05 to about 50, and most preferably 0.1 to 30 gfeed/g catalyst/hour. The hydrogen-containing fluid (gas) hourly spacevelocity generally is in the range of about 1 to about 10,000,preferably about 5 to about 7,000, and most preferably 10 to 10,000 ft³H₂ /ft³ catalyst/hour. Generally, the pressure can be in the range offrom about 10 to about 2000 psig, preferably about 100 to about 1000psig, and most preferably 200 to 750 psig, and the temperature is about250 to about 1000° C., preferably about 300 to about 750° C., and mostpreferably 400 to 650° C.

The process effluent generally contains a light gas fraction comprisinghydrogen and methane; a C₂ -C₃ fraction containing ethylene, propylene,ethane, and propane; an intermediate fraction including non-aromaticcompounds having greater than 3 carbon atoms; a BTX aromatichydrocarbons fraction (benzene, toluene, ortho-xylene, meta-xylene andpara-xylene); and a C₉ +fraction which contains aromatic compoundshaving 9 or more carbon atoms per molecule. Generally, the effluent canbe separated into these principal fractions by any known methods suchas, for example, fractionation distillation. Because the separationmethods are well known to one skilled in the art, the description ofwhich is omitted herein. The intermediate fraction can be fed to anaromatization reactor to be converted to aromatic hydrocarbons; methane,ethane, and propane can be used as fuel gas or as a feed for otherreactions such as, for example, in a thermal cracking process to produceethylene and propylene. The olefins can be recovered and furtherseparated into individual olefins by any method known to one skilled inthe art. The individual olefins can then be recovered and marketed. TheBTX fraction can be further separated into individual C₆ to C₈ aromatichydrocarbon fractions. Alternatively, the BTX fraction can furtherundergo one or more reactions either before or after separation toindividual C₆ to C₈ hydrocarbons so as to increase the content of themost desired BTX aromatic hydrocarbon. Suitable examples of suchsubsequent C₆ to C₈ aromatic hydrocarbon conversions aredisproportionation of toluene (to form benzene and xylenes),transalkylation of benzene and xylenes (to form toluene), andisomerization of meta-xylene and/or ortho-xylene to para-xylene.

After the catalyst composition has been deactivated by, for example,coke deposition or feed poisons, to an extent that the feed conversionand/or the selectivity to the desired ratios of olefins to BTX havebecome unsatisfactory, the catalyst composition can be reactivated byany means known to one skilled in the art such as, for example,calcining in air to burn off deposited coke and other carbonaceousmaterials, such as oligomers or polymers, preferably at a temperature ofabout 400 to about 1000° C. The optimal time periods of the calciningdepend generally on the types and amounts of deactivating deposits onthe catalyst composition and on the calcination temperatures. Theseoptimal time periods can easily be determined by those possessingordinary skills in the art and are omitted herein for the interest ofbrevity.

The following examples are presented to further illustrate thisinvention and are not to be construed as unduly limiting the scope ofthe present invention.

EXAMPLE I

This example illustrates the effect of the treatment of a beta zeolitematerial with steam essentially according to the second embodiment ofthe invention.

A commercial beta zeolite BEA, which was provided by UOP (Des Plains,Ill.) as 1/16 inch extrudes, was used in the Examples. This material (10g) was impregnated with an ammonium molybdate solution containing 0.375g ammonium molybdate ((NH₄)₆ MO₇ O₂₄.4H₂ O) and 6 g H₂ O by the wellknown incipient wetness method at about 25 ° C. The ammoniummolybdate-impregnated beta zeolite was then calcined in air (mufflefurnace) for 6 hours at 538° C. to produce 10.01 g of catalyst Acontaining 2.036 weight % molybdenum by calculation.

In a separate run, 33.50 g of the commercial beta zeolite treated with100 ml of an aqueous 6N HCl solution (i.e., an aqueous solutioncontaining 6 g-equivalents of hydrochloric acid) for 1 hour at 94° C.The mixture of acid-treated beta zeolite material and HCl solution wasfiltered, washed with running water for about 30 minutes and then heatedat 525 ° C. for 6 hours to produce 22.75 g of an acid-leached betazeolite. The acid-leached beta zeolite (5.01 g) was then impregnatedwith a solution containing 5.22 g of 6 weight % ammonium heptamolybdate((NH₄)₆ MO₇ O₂₄.4H₂ O) solution by the well-known incipient wetnessmethod described above. The impregnated beta zeolite was calcined in airfor 6 hours at 538° C. to produce 5.07 g Mo-promoted, acid-leached betazeolite (catalyst B) containing 3.357 weight % Mo by calculation.

Catalyst C was obtained by first heating 33.50 g of beta zeolite withsteam at 425° C. for 2 hours to produce a steamed zeolite. The steamedzeolite, upon being cooled with a helium flow to 25° C., was treatedwith 1N HNO₃ for 2 hours at 95° C. followed by drying in air at 525° C.for 6 hours to produce 31.32 g of a steamed, acid-leached beta zeolite.Thereafter, 6.65 g of the acid-leached beta zeolite was impregnated with4.23 g of a 6 weight % ammonium heptamolybdate solution followed by aircalcining at 538° C. for 6 hours to produce a product weighing 6.47 gand contained 2.132 weight % molybdenum by calculation.

EXAMPLE II

This example illustrates the use of the zeolite materials (catalysts A,B, and C) described in Example I in the transalklylation of a feedcomprising C₉ +aromatic compounds and toluene to produce a productcontaining a higher concentration of BTX than the feed. The compositionof aromatic compounds, up to 12 carbon atoms per molecule, of the feedused for the transalkylation is shown in Table I. There were numerousunidentified components in the feed that are not shown in thecalculation disclosed in Table I.

                  TABLE I                                                         ______________________________________                                        Composition         Weight %                                                  ______________________________________                                        Paraffins               2.032                                                 i-Paraffins             9.255                                                 Naphthenes              1.267                                                                  Total                                                        Aromatics        C.sub.6                                                                              0.000                                                                  C.sub.7                                                                              50.248                                                                 C.sub.8                                                                              0.411                                                                  C.sub.9                                                                              11.315                                                                 C.sub.10                                                                             12.664                                                                 C.sub.11                                                                             9.457                                                                  C.sub.12                                                                             3.001                                                                  Total  87.096                                                Sulfur (ppmw)           658                                                   ______________________________________                                    

A stainless-steel reactor tube (inner diameter: 2.5 cm; length: 50 cm)was filled with a 20 cm bottom layer of Alundum® alumina (inert, lowsurface area alumina, provided by Norton Company, Worcester, Mass.), 5ml of one of the zeolite materials described in Example I, and a 20 cmtop layer of Alundum®. The reactor and its content were pre-heated fromroom temperature to the desired reaction temperature of about 575° C.The zeolite materials (catalysts) were pretreated with flowing hydrogengas at a rate of 260 ml per minute at 500° C. starting at 25° C. andramping at 10° C./min. The reaction pressure was set at 500 psig. Aliquid feed as shown in Table I was introduced into the heated reactorat a rate of 20 ml/hour, which was equivalent to a hourly space velocityof about 5.6 ml/ml catalyst/hour. The product, which exited the reactor,was cooled, analyzed by means of an online gas chromatograph atintervals of about 1 hour. Pertinent test results are summarized inTable II. The zeolite materials (catalysts) were also used in ahydrodealkylation of C₉ +aromatic compounds. The results are alsosummarized in Table II.

                                      TABLE II                                    __________________________________________________________________________            Time.sup.c                                                                        Temp                                                                              % Conv                                                                            % Conv.sup.4                                                                       wt %                                                                              wt %                                                                              Avg wt %                                     Catal.sup.a                                                                       Pretmt.sup.b                                                                      (hr)                                                                              (° C.)                                                                     C.sub.9 +                                                                         Naph C.sub.1 -C.sub.6                                                                  Xyln's                                                                            Coke/hr.sup.f                                __________________________________________________________________________    A   None                                                                              7.00                                                                              503 45.4                                                                              33.0 3.1 7.1 2.555                                        B   AL  7.28                                                                              497 78.1                                                                              78.1 13.2                                                                              24.0                                                                              2.250                                        C   425; AL                                                                           6.69                                                                              499 80.3                                                                              83.8 14.7                                                                              24.0                                                                              1.20                                         __________________________________________________________________________     .sup.a See catalyst designations in Example I.                                .sup.b Pretreatment of beta zeolite with an acid (AL) or steam at             temperatures indicated.                                                       .sup.c Time of transalkylation reaction.                                      .sup.d Conversion of naphthalenes.                                            .sup.e Coke was determined at the end of the reaction by removing the         catalysts from the reactor and determined with a thermal gravimetric          analyzer (TGA), manufactured by TA Instruments, New Castle, Delaware.    

The results shown in Table II demonstrate that a beta zeolitepre-treated with steam followed by acid-leaching before beingimpregnated with a metal compound significantly improved the conversionof C₉ +aromatic compounds, including naphthalenes, to xylenes andsignificantly reduced the coke rate in a transalkylation process(comparing catalyst C with A). The results also show that acid-leachinga beta zeolite followed by impregnating a metal compound onto theacid-leached beta zeolite (catalyst B) also significantly improved theconversion of C₉ +aromatic compounds to xylenes, though the reduction incoking rate was not as profound as catalyst C.

The results shown in the above examples clearly demonstrate that thepresent invention is well adapted to carry out the objects and attainthe ends and advantages mentioned as well as those inherent therein.While modifications may be made by those skilled in the art, suchmodifications are encompassed within the spirit of the present inventionas defined by the disclosure and the claims.

That which is claimed:
 1. A process consisting essentially of:(1)contacting a beta zeolite with steam at a temperature in the range offrom about 200° C. to about 1000° to produce a steamed beta zeolite; (2)contacting said steamed beta zeolite with an aqueous solution containingan acid at a pH lower than about 6, at a temperature in the range offrom about 30 to about 200° C., under about 1 to about 10 atm pressure,and for a period of from about 10 minutes to about 30 hours to producean acid-leached Beta zeolite; (3) contacting said acid-leached betazeolite with a metal compound thereby producing a metal-promoted betazeolite by a method chosen from incorporating said metal into saidacid-leached beta zeolite or impregnating said acid-leached beta zeolitewith said metal; (4) calcining said metal -promoted beta zeolite whereinthe metal of said compound is selected from the group consisting ofnickel, palladium, molybdenum, gallium, platinum, tungsten, tin, indium,chromium, rhodium, rhenium, cobalt, germanium, zirconium, titanium,ruthenium, and combinations of any two or more thereof and said acid isselected from the group consisting of sulfuric acid, hydrochloric acid,nitric acid, phosphoric acid, formic acid, acetic acid, trifluoroaceticacid, trichloroacetic acid, p-toluenesulfonic acid, methanesulfonicacid, partially neutralized acids, and combinations of any two or morethereof.
 2. A process according to claim 1 further comprising contactingsaid steamed beta zeolite with an acid thereby reducing the aluminumcontent of the beta zeolite to produce an acid-leached beta zeolite;and, thereafter, contacting said acid-leached beta zeolite with saidmetal compound to produce a metal-promoted beta zeolite.
 3. A processaccording to claim 2 further comprising treating the metal-promoted betazeolite with a reducing agent thereby lowering the oxidation state ofsaid metal associated with the metal-promoted beta zeolite.
 4. A processaccording to claim 2 wherein said acid is selected from nitric acid,hydrochloric acid, and combinations thereof.
 5. A process according toclaim 2 wherein the metal of said metal compound is molybdenum.
 6. Aprocess according to claim 2 wherein said metal compound is ammoniummolybdate.
 7. A process according to claim 1 further comprising treatingthe metal-promoted beta zeolite with a reducing agent thereby loweringthe oxidation state of said metal associated with the metal-promotedbeta zeolite.
 8. A process according to claim 1 wherein said acid isselected from the group consisting of sulfuric acid, hydrochloric acid,nitric acid, phosphoric acid, formic acid, acetic acid, trifluoroaceticacid, trichloroacetic acid, p-toluenesulfonic acid, methanesulfonicacid, partially neutralized acids, and combinations of any two or morethereof.
 9. A process consisting essentially of:(1) contacting a betazeolite with steam thereby producing a beta zeolite having a reducedcoking rate in a transalkylation process to produce a steamed betazeolite; (2) contacting said steamed beta zeolite with an acid therebyreducing the aluminum content of said beta zeolite to produce anacid-leached beta zeolite; and (3) contacting said acid-leached betazeolite with a metal compound thereby incorporating said metal compoundinto said acid-leached beta zeolite to produce a metal-promoted betazeolite.
 10. A process according to claim 9 further comprisingcontacting said metal-promoted beta zeolite with a reducing agentthereby lowering the oxidation state of said metal in the metal-promotedbeta zeolite.
 11. A process according to claim 10 wherein the metal ofsaid metal compound is selected from the group consisting of nickel,palladium, molybdenum, gallium, platinum, tin, chromium, rhodium,rhenium, tungsten, indium, cobalt, germanium, zirconium, titanium,ruthenium, and combinations of any two or more thereof.
 12. A processaccording to claim 10 wherein said metal compound is ammonium molybdate.13. A process according to claim 9 wherein said acid is selected fromthe group consisting of sulfuric acid, hydrochloric acid, nitric acid,phosphoric acid, formic acid, acetic acid, trifluoroacetic acid,trichloroacetic acid, p-toluenesulfonic acid, methanesulfonic acid,partially neutralized acids, and combinations of any two or morethereof.
 14. A process according to claim 9 wherein said acid isselected from the group consisting of nitric acid, hydrochloric acid,and combinations thereof.
 15. A process according to claim 9 wherein themetal of said metal compound is selected from the group consisting ofnickel, palladium, molybdenum, gallium, platinum, tin, chromium,rhodium, rhenium, tungsten, indium, cobalt, germanium, zirconium,titanium, ruthenium, and combinations of any two or more thereof.
 16. Aprocess according to claim 9 wherein the metal of said metal compound ismolybdenum.
 17. A process according to claim 9 wherein said metalcompound is ammonium molybdate.
 18. A process according to claim 9whereinthe metal of said metal compound is selected from the groupconsisting of nickel, palladium, molybdenum, gallium, platinum, tin,chromium, rhodium, rhenium, tungsten, indium, cobalt, germanium,zirconium, titanium, ruthenium, and combinations of any two or morethereof; and said acid is selected from the group consisting of sulfuricacid, hydrochloric acid, nitric acid, phosphoric acid, formic acid,acetic acid, trifluoroacetic acid, trichloroacetic acid,p-toluenesulfonic acid, methanesulfonic acid, partially neutralizedacids, and combinations of any two or more thereof.
 19. A processaccording to claim 18 further comprising treating said metal-promotedbeta zeolite with a reducing agent thereby lowering the oxidation stateof said metal in said metal-promoted beta zeolite.
 20. A processaccording to claim 19 wherein said metal compound is ammonium molybdate.21. A process according to claim 18 wherein said metal compound isammonium molybdate.
 22. A process consisting essentially of: (1)contacting a beta zeolite with steam at a temperature in the range offrom 350 to 625° C. to produce a steamed beta zeolite; (2) contactingsaid steamed beta zeolite with an aqueous solution of hydrochloric acidor nitric acid at a temperature in the range of from about 70 to about100° C., under about 1 to about 10 atm pressure, and for a period offrom 1 to 20 hours to produce an acid-leached beta zeolite; (3)impregnating said acid-leached beta zeolite with an aqueous ammoniummolybdate solution thereby producing a molybdenum-promoted beta zeolite;and (4) calcining said molybdenum-promoted beta zeolite at 450° C. to650° C. for 2 to 15 hours.